🧷 Authentic Classroom Explanation by IAS Monk

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📌 The Question:

‘Microsatellite DNA’ is used in the case of which one of the following?

(a) Studying the evolutionary relationships among various species of fauna
(b) Stimulating stem cells to transform into diverse functional tissues
(c) Promoting clonal propagation of horticultural plants
(d) Assessing the efficacy of drugs by conducting series of drug trials in a population

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✅ Answer: (a) Studying the evolutionary relationships among various species of fauna

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🧑‍🏫 Classroom Explanation:

Microsatellite DNA, also known as Short Tandem Repeats (STRs), consists of short DNA sequences (1–6 base pairs) repeated multiple times at specific genomic locations.

Key properties:

• Highly polymorphic (variation in repeat number)
• Mostly non-coding
• Easily amplified using PCR

🔹 Why option (a) is correct ✅
Because microsatellites show high variability across individuals and populations, they are excellent molecular markers for:

• Population genetics
• Evolutionary biology
• Phylogenetic relationships
• DNA fingerprinting

They help trace genetic diversity, lineage, and evolutionary distances among species.

🔹 Why other options are incorrect ❌

• (b) Stem cell differentiation involves growth factors and gene regulation, not microsatellites
• (c) Clonal propagation relies on tissue culture techniques
• (d) Drug trials involve biostatistics and pharmacology, not STR analysis

Hence, option (a) is correct.

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🔍 Curiosity Raiser:

🧬 Why do forensic scientists love microsatellites?
Because even close relatives rarely share the same STR pattern.

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📚 Enrichment Notes (UPSC Edge):

• Microsatellites are widely used in:
  • Forensic science
  • Wildlife conservation genetics
  • Paternity testing
• They became popular with the rise of PCR technology in the 1990s
• Neutral evolutionary history makes them ideal for population studies

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🧘 IAS Monk Whisper:

🌱 Tiny repetitions in DNA can narrate the grand story of evolution.